00 introductory comments

CN3132

SSEEPPAARRAATTIIOONN PPRROOCCEESSSSEESS

CN3132 is a core chemical engineering module to introduce design concepts of industrially relevant separation processes

Prerequisite: CN 1111, CN2125

S Farooq Department of Chemical & Biomolecular Engineering

Office: E5-02-26 Phone: 6516 6545

Email: [email protected]

Farooq/CN3132/Introduction-2

Flippedclassroom

We will adopt flipped classroom approach. Detailedlectureswillbeuploadedasonlinevideos.Youmustviewthevideosbeforecomingtotheclass.

In theclass, the focuswillbemoreonkeyconceptsanddesignissues.

More timewillbe spenton illustrations through solvingproblems.

Youwillberequiredtoactivelyparticipate.


Topicstobecoveredinthisvideo Compulsory reading: Chapter 1 from the text book

Why study separation? About the module Learning objectives Expected outcomes Course content and mode of delivery Text book and supporting materials Schedules

Mechanism of mass transfer Equilibrium design method


Importanceofseparation5090%ofthecapitalinvestedinachemicalplantgoestoseparationequipment

Atypicalchemicalplant

Undesirableimpuritiesremovedfromtherawmaterialbeforereaction Separationofproductfromunreactedfeedforrecycling Furtherpurificationofproduct(s)tomeetthecustomerspecification


Processflowdiagramofformaldehydemanufacturefrommethanol

DISTILLATION


Productionofpetroleum/petrochemicalproductsfromcrudeoilinarefinery Watch the video at the following location to know more about various products from a refinery distillation column: http://www.youtube.com/watch?feature=player_detailpage&v=c2XV0Qk7PEU


Penicillinproduction(Biotechnology) Environmentalprotection(H2SRemoval)

Canyouidentifytheseparators? Whatarethemostcommonseparators?


Technicalvs.UseMaturitiesofSeparationProcesses


LearningobjectivesPre-requisites: Equilibrium and mass balance concepts introduced in

CN 1111 and CN2125

Thestudentswilllearnthedesignandoperationofstandardequilibriumstageseparationprocessesusedinthechemicalindustries

ExpectedOutcomesAt the end of the course the students are expected to

Explain equilibrium concepts in separation. Describe the effects of various operating variables on the separation

output. Design, analyze, troubleshoot and improve standard separation processes

used in chemical industries. Make informed choices among alternatives in the design and operation of

separation processes.


Coursecontent

Date 90minutelecture (Monday) 45minutelecture (Thursday) Watchuploadedvideolecturebeforetheface

tofacelecture

Comment

10August Holiday13August BinaryFlashDistillation Yes 15August Makeupforthelecture

lostonAugust10Venue:LT5Time:11amto1pmTopic:BinaryFlash

Distillation17August MulticomponentFlash/

BinaryMultistagedistillation

Yes

20August BinaryMultistageDistillation24August BinaryMultistage

Distillation27August BinaryMultistageDistillation Yes 31August Absorption 3Sept Absorption 7Sept Absorption/

Extraction(immisciblesystem)

Yes

10Sept Extraction14Sept Extraction(misciblesystem) 17Sept Extraction(misciblesystem) 28Sept Multicomponentdistillation 1Oct Midtermtest Time:8:45amto9:45am

Venuetobeannouncedlater

NOTE:LecturetimehasnotbeenassignedforthetopicColumndesign.Recordedlecturewillbeuploadedtocoverthistopic.


Dr Dan Zhao will take over after October 1 and cover the following topics Rate Based Design of Continuous Contact Processes Simultaneous Heat and Mass Transfer Adsorption Processes


Coursematerials Text book and supporting books (No. 1 is the prescribed text):

1. Wankat, P.C., Separation Process Engineering, Prentice Hall, 3nd Edition (2012)

2. Treybal, R.E., Mass-Transfer Operations, McGraw-Hill, International Edition (1980).

Course Notes

Every student must have a text book and read the relevant chapters. Course notes should only be used as complimentary materials - not a substitute for the text book.

Video Clips uploaded and links provided in the lecture notes

Philip C. Wankat

2nd Edition 3rd Edition


Assessment

Home work every week Home work problems will be discussed in the tutorials Homework problems will not be graded, but tested orally

Continual assessment (CA) (Open book: Text book and lecture notes) Formative: Short questions on topics covered in previous lecture(s)

for self-assessment Summative: 1 term test after the term break

(schedule on the next page) :20%

Final examination (Open book: Text book and lecture notes) 2.5 hours Compulsory questions

Final mark = 20% CA (S. Farooqs part) + 20% CA (Dr. Zhaos part) + 60% Final examination

Objective is to help develop skill for solving design problems

Objective is to test the basic concepts, apply a simple design method to a real process, encourage team work and practice presentation skill

Test overall learning of the expected outcomes


Schedulesforlectures,tutorials,consultationandclasstests Lectures

Venues: LT6: Monday: 9 am 10:45 am Thursday: 9 am 9:45 am

20 lectures over 7 weeks 3 lectures per week

Tutorials

1 tutorial per group per week Consultation

Wednesdays from 5 pm 7 pm in my office (E5-02-26) no appointment necessary

By email By appointment on other days

Test date Topics to be covered

Oct 1, 2015 All the topics

Test

Venue: TBA Time: 8:45 am to 9:30 am


Mechanismofdiffusionalmasstransfer

Test your intuition (Assumption: Solubility of air in water is negligible compared to CO2) Essential features?

There should be at least two phases.

Separation takes place through inter-phase mass transfer

Mass Transfer is at the molecular scale. There is no visible bulk movement as a result of mass transfer.

Inter-phase mass transfer is affected by - Phase equilibrium (Thermodynamics) Driving Force - Interfacial area available for phase contact - Molecular diffusion (Mass Transfer) - Mixing/ Convection (Fluid Mechanics) - Contact time

Rate of Mass Transfer

Which arrangement will give the lowest CO2 concentration in exit air?

What will happen if water height is increased?

What is the upper limit? Give reasons to whatever

your answers are..

Air + CO2 Air + depleted CO2

Water Water

Glass bead

Air bubble

Air + CO2 Air + depleted CO2

Air + CO2

Air + depleted CO2


Tray Tower Packed Tower

Contactingofphases

Direct contact vs. Phases Separated by a Membrane

Direct contact is most common

Phase combination Example Vapor-Liquid Gas Liquid

Distillation Absorption

Gas Solid Adsorption Liquid Liquid Extraction Liquid Solid Leaching,

Adsorption

Staged contact - example is tray tower Continuous contact example is packed tower

See the videos to visualize mixing patterns and different types of trays at the link below:

http://courses.nus.edu.sg/course/chesf/cn2113/UO/UO_SeparationProcess/ Membrane separations are rapidly gaining importance.


Tray Tower vs. Packed Tower

1. Gas-pressure drop. Pressure drop is less in packed towers. Low pressure drop is Important for vacuum distillation. 2. Liquid holdup. Packed towers haves substantially smaller liquid holdup. This is important where liquid deterioration occurs with

high temperatures and short holding times are essential. It is also important for sharp separations in batch distillation. 3. Liquid/gas ratio. Very low values of this ratio are best handled in tray towers. High values are best handled in packed towers. 4. Liquid cooling. Cooling coils are more readily built into tray towers; and liquid can more readily be removed from trays, to be

passed through coolers and returned, than from packed towers. 5. Side streams. These are more readily removed from tray towers. 6. Foaming systems. Packed towers have less bubbling of gas through the liquid and are more suitable for foaming liquid. 7. Corrosion. Packed towers for difficult corrosion problems are likely to be less costly. 8. Solids present. Neither type of tower is very satisfactory. Agitated vessels and venturi scrubbers are best but provide only a

single stage. If multistage countercurrent action is required, it is best to remove the solids first. 9. Cleaning. Frequent cleaning is easier with tray towers. 10. Large temperature fluctuations. Fragile packing (ceramic, graphite) tend to be crushed. Tray or metal packing is satisfactory. 11. Floor loading. Plastic packed towers are lighter in weight than tray towers which in turn are lighter than ceramic or metal packed

towers. In any event, floor loadings should be designed for accidental complete filling of the tower with liquid. 12. Cost. If there is no overriding consideration, cost is the major factor to be taken into account. 13. Minimum diameter. Tray tower has a minimum diameter limit of 0.6 m.


Equilibriumdesignmethod There are two main design concepts for mass transfer processes: Equilibrium stage Rate based (To be covered by Dr. Dan Zhao)

Equilibrium stage concept applies to both tray and packed towers We illustrate the concept with a tray tower for a clear physical understanding

Each tray is a stage IDEAL STAGE Streams leaving from each ideal stage are in equilibrium

Liquid flow

Rising vapor/gas

Perforatedtray

IDEAL STAGE

Lin

Lout Vin

Vout

The main feature of the equilibrium design concept is Lout and Vout are in equilibrium


Complete equilibrium is not achieved in a real operation STAGE/TRAY EFFICIENCY used to account for not achieving complete equilibrium

Actual number of trays required =

Empirical plots are available for stage efficiency calculations. Design companies use in-house data

Column height is related to the actual number of trays Column diameter depends on required processing rate and maximum allowable velocity Material balances determine the quantity of the different streams required There are maximum allowable velocity limits based on hydrodynamic considerations

Problem-solving methods: Usefulness of the discussion in section 1.4 goes beyond this module.

No. of IDEAL STAGES STAGE EFFICIENCY

00 introductory comments

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